Dual level tilting tray package sorting apparatus

ABSTRACT

An automatic system for sorting items, such as small parcels, into groups bound for different geographical locations is described. The system uses tilting trays arranged at multiple levels, with all the trays being mounted on carriages traveling on a single monorail. The trays are tilted at the proper output chutes by cam roller mechanisms which are appropriately inserted into the path of cams on the trays under the coordination of a digital controller. A simple drive mechanism moves the carriages along the monorail using a drive roller which presses against the carriages. The carriages may be linked by a pliable linkage assembly that does not include mechanical hinges or like mechanisms. The system is easy to repair and operates at low noise levels.

TECHNICAL FIELD

The present invention relates to automatic sorting of items such assmall packages into groups bound for different geographical locations,and more particularly relates to an automatic sorting apparatus usingtilting trays which receive items from input conveyors and deposit theminto designated output chutes or bins under programmed control.

BACKGROUND ART

Tilt tray sorters have been available for many years. Such systems areuseful in sorting small packages for delivery to different regions, suchas zip code areas. Under control of a computer or programmed logiccontroller, packages may be identified or coded as they enter thesystem, and then tracked for output at a chute or bin corresponding tothe coded destination.

It is known to form a loop of linked carriages running along a loop oftrack. A human operator or automatic equipment loads items onto traysmounted on the carriages at one point around the loop, and the systemautomatically tilts the trays at various output locations adjacent tothe track to discharge the packages. Many such systems drive the linkedcarriages by means of a chain or belt drive, which tends to be expensiveand noisy. Such systems also occupy a large amount of space, and includecomplex mechanisms that are relatively difficult to repair.

At a package delivery company, the amount of time a sorter is shut downfor repairs has a significant negative effect on the company's abilityto meet delivery deadlines. Thus, reliability is a major goal indesigning sorting systems. By simplifying mechanical assemblies andproviding for easy substitution of failed parts, reliability can beincreased and down time reduced. Furthermore, such companies must takesteps to reduce noise levels in their facilities as governmentalregulations concerning noise become more strict; thus, lowering noiselevels in sorting systems is also a major goal.

The sorting system disclosed in U.S. Pat. No. 4,712,965 drives linkedcarriages around a dual rail track by means of one or more drivecarriages. The drive carriages contain motors which derive power foroperation from sliding contacts. The motors drive rollers which arepressed against a third rail by the weight of the motor. The carriagesare separated by bumpers, and unloading is accomplished by drivenconveyor belts mounted on the carriages, rather than by tilting trays.

Another system of looped carriages, but including a tilting traymechanism, is disclosed in U.S. Pat. No. 5,054,601, which isincorporated herein by reference. The carriages are driven by inductionmotors positioned beneath the path of the carriages. A conveyor andoverhead loader mechanism automatically load the carriages and shaftencoders monitor the speed of the carriages along the looped track.Rollers mounted on the carriages interact with cams provided along thetrack to unload the trays at their predetermined destination. Theloading and unloading functions are under computer control. A latchmechanism holds the trays in a tilted position until they arestraightened by a return mechanism.

In those prior art systems which drive a series of carriages by means ofa chain or belt positively connected to the carriages, there is no needto link the carriages. In fact they may be spaced apart along the chainto avoid interaction. However, in some prior systems in which the trainof carriages has been pulled by a locomotive carriage or by induction,the carriages must be linked. The linkage between carriages is a sourceof wear and noise. Therefore, a mechanical joint consisting of multipleinteracting metal or plastic parts must be designed to reduce frictionand possibly lubricated. Even then, the wear and noise problemsassociated with each linkage can only be alleviated, not eliminated.

Tilting tray sorting systems are also shown in U.S. Pat. Nos. 4,089,404;5,018,928; and 4,982,828. The latter patent discloses a mechanism whichtilts the trays by moving rollers mounted along the track into the pathof cam surfaces on the edges of the trays.

Another problem which arises in the field of automatic sorting is how tohandle and sort large, irregularly shaped items. The prior systems notedabove generally are unable to handle such irregular items.

As may be seen from the foregoing, prior sorting systems are complexboth mechanically and electrically, require a relatively large amount offloor space for the volume of items that can be sorted, requiresignificant maintenance, and by their nature are noisy. There has been aneed in the art for a sorting system that is simple in construction, iseasy to maintain and keep on line, provides a high throughput of sorteditems per occupied floor space, and operates at low noise levels.

SUMMARY OF THE INVENTION

The present invention provides an improved sorting system which uses asimple, inexpensive construction, may be easily maintained bysubstitution of components, increases throughput by providing a doubletier of tiltable trays, employs a unique drive mechanism, and decreasesnoise levels by employing a flexing linkage with no moving parts betweencarriages and by employing a low-noise drive mechanism. These featuresindividually and in combination are aspects of the present invention.

Generally described, one aspect of the invention provides an apparatusfor transporting objects, comprising a track, a plurality of carriageseach including a carriage body mounted for movement along the track, atleast one of the carriages including an upper object-holding platformspaced above the body, and at least one of the carriages including alower object-holding platform positioned below the level of the upperplatform, and a drive mechanism operable to cause the carriages to movealong the track. Preferably, one of the carriages is an upper levelcarriage including only an upper object-holding platform, and at leastone of the carriages is a lower level carriage including only a lowerobject-holding platform positioned below the level of the upperplatform. In this preferred arrangement, the carriages are arranged toalternate upper and lower level carriages, and the upper platformsextend at least partly over the lower platforms of adjacent lower levelcarriages.

The carriages may be positioned to occupy all of a closed loop withoutany linkage between carriages, or, if desired, they may be linkedtogether.

Another aspect of the present invention provides an apparatus fortransporting and sorting objects, each to one of a plurality of outputlocations, comprising a track, a plurality of carriages mounted adjacentto one another for movement along the track, a drive mechanism includinga drive roller mounted adjacent to the track to frictionally engage thecarriages in sequence and a source of rotational force mounted to rotatethe drive roller so as to cause the carriages to move along the track, atransfer mechanism operative to unload an object from the carriages, atleast one sensor located to monitor the position of each of thecarriages along the track, and a programmed controller configured tooperate the transfer mechanism responsive to the sensor to unload acarriage carrying an object when the carriage reaches a predeterminedoutput location along the track. Optionally, the drive mechanismcomprises two or more of the drive rollers spaced apart from oneanother. The source of rotational force may comprise a motor connectedto the drive roller by a drive shaft pivotally mounted about an axislocated intermediate the drive roller and the motor, with the driveroller and the motor being movable with the drive shaft such that theweight of the motor urges the drive roller against the carriages.

Another aspect of the present invention provides an apparatus fortransporting objects, comprising a track, a plurality of carriagesmounted for movement along the track, a drive mechanism operable tocause the carriages to move along the track, and a linkage connectingadjacent carriages, the linkage comprising a bracket attached to each ofthe adjacent carriages, shaped to define a pocket, and a link memberdefining a pair of ends positioned in the pockets. The brackets arepreferably positioned on side surfaces of the carriages, with thepockets opening to face an adjacent carriage. Furthermore, the linkmember may be made of pliable material and may include a cushioningmember extending between end surfaces of the carriages.

In the foregoing aspects of the present invention, an object holdingplatform associated with the carriages may be provided with a camsurface, and a transfer mechanism comprising a cam follower may beselectively positionable in the path of the cam surface.

Another aspect of the present invention provides an apparatus fortransporting objects, comprising a track, a plurality of carriagesmounted for movement along the track, a drive mechanism operable to movea line of the carriages along the track, and an object-holding platformsuspended below at least two of the carriages and movable with the lineof carriages. A transfer mechanism operable to remove an object from theplatform may be provided and may include a conveyor or means forselectively tilting the platform.

Thus, it is an object of the present invention to provide an improvedautomated sorting system.

It is a further object of the present invention to provide a sortingsystem for small items or packages which sorts such items at a high rateper floor area occupied by the system.

It is a further object of the present invention to provide atransportation system of the type including a line of carriages, havingan uncomplicated drive system which requires neither a drive chain orbelt nor a propulsion mechanism mounted on board any carriage.

It is a further object of the present invention to provide atransportation system of the type including carriages linked to oneanother in a way which both cushions the carriages from one another andpermits relative movement without a multi-part joint.

It is a further object of the present invention to provide an automatedtransportation system which operates at a low noise level.

It is a further object of the present invention to provide an automatedtransportation system that can be repaired by replacing inexpensivesub-assemblies.

It is a further object of the present invention to provide an automatedsorting system that is suitable for carrying and sorting large,irregular items.

Other objects, features, and advantages of the present invention willbecome apparent upon review of the following description of preferredembodiments and the appended drawing and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic top plan view of a sorting system embodying theinvention.

FIG. 2 is a pictorial view of the sorting system of claim 1, with pansremoved to show detail.

FIG. 3 is a end view of a carriage of the sorting system of claim 1,also showing the tilting actuator and drive mechanism.

FIG. 4 is a outer side elevation view of a section of the sorting systemof claim 1, with parts broken away to show interior detail.

FIG. 5 is a end elevation view of a carriage with the tilting actuatorpositioned to tilt the tray.

FIG. 6 is a diagrammatic view of a cam surface of a tray interactingwith a cam follower of the tilting mechanism.

FIG. 7 is a diagrammatic view of a cam surface of a tray interactingwith a cam follower of the tilting mechanism at a time subsequent tothat shown in FIG. 6.

FIG. 8 is a diagrammatic view of an alternate embodiment of a tray camsurface for use with carriages that can travel in reverse.

FIG. 9 is a end elevation view of a pair of adjacent carriages (upperand lower) aligned with input conveyors.

FIG. 10 is a end elevation view of a pair of adjacent carriages (upperand lower), the trays of which have been tilted for depositing parcelsonto output conveyors.

FIG. 11 is a diagrammatic top plan view of adjacent carriages linked byflexible bumpers.

FIG. 12 is side view of the carriages of FIG. 11.

FIG. 13 is a pictorial view of a flexible bumper being inserted intobrackets mounted on adjacent carriages.

FIG. 14 is a side view of a removable rail section.

FIG. 15 is an end view of the attachment of the removable section ofFIG. 14 to a post.

FIG. 16 is an end elevation view of an alternate rail construction.

FIG. 17 is a diagrammatic side view of a second embodiment of a sortingsystem utilizing suspended platforms.

FIG. 18 is an end sectional view of the sorting system of FIG. 17.

FIG. 19 is an end view of a suspended platform including motorizedrollers for unloading items.

FIG. 20 is an end view of a suspended platform including a motorizedconveyor for unloading items.

FIG. 21 is a flow chart outlining operation of the sorting system undercontrol of a digital controller.

DETAILED DESCRIPTION

Referring now in more detail to the drawing, in which like numeralsrefer to like parts throughout the several views, FIG. 1 shows anautomatic sorting system 10 embodying the present invention. Withreference to FIGS. 1 and 2, the sorting system 10 includes a monorail 12and a line or train of carriages 14 mounted for travel along themonorail 12. In the preferred form shown, the monorail forms a closedloop, and the carriages fill the monorail. Thus, the carriages 14 may bedriven along the monorail in one direction by a drive mechanism 16, tobe described in detail below. The carriages 14 travel through an inputsection 18 at which they are loaded with items, such as parcels to bedelivered to addressee destinations, and then through output sections20. At the output sections 20, the items are removed from the carriagesby tilting mechanisms 22 which remove the items at an output chutecorresponding to the item's destination, in a manner described below.

Other subassemblies of the sorting system 10 shown in FIG. 1 include areturn mechanism 24, which prepares the carriages to receive new itemsas they return to the input section 18, and a carriage tracking station26 which positively locates a carriage carrying a particular item sothat a controller (not shown) including a digital processor may causethe item to be sorted to the correct destination. The subassemblies thusfar noted and shown diagrammatically in FIG. 1 will now be described indetail.

Referring now to FIG. 3, the monorail 12 is supported by a plurality ofsupport posts 30. A suspending bracket 32 extends from each post 30 andis attached, such as by welding, to the monorail 12, to hold themonorail 12 in a position spaced horizontally from the posts 30. In thepreferred embodiment shown, the monorail 12 consists of a square steelextrusion held by the brackets 32 in a diamond configuration, that is,with opposing comers of the square cross section aligned vertically.Other metals or suitably strong materials may be utilized, and the beammay be hollow as shown or solid. An alternate embodiment of a monorail34, designed for greater stability, is shown in FIG. 16. In thisembodiment, a rectangular box beam 35 is attached to the posts 30 by aflanged support bracket 38. L-shaped extrusions or angle irons 36 arewelded to the top and bottom surfaces of the box beam 35. Thus, themodified monorail 34 is an extended version of the square monorail 12.

A removable section 40 of the monorail 12 is shown in FIGS. 14 and 15. Apair of special suspending brackets 42 are attached to the ends of theremovable section 40 and the main monorail 12. Both of the brackets 42are bolted to a slotted bracket 43 which is attached to the post 30. Thebrackets 42 slide into a slot 44 formed in the bracket 43, and are heldin place by bolts 45 which pass through mating holes in the brackets 42and 43. By removing the bolt 45 which attaches the removable section tothe post 30, the removable section 40 can be slid out of the slot 44 inorder to remove and replace carriages on the monorail 12. This procedurereduces down time in repairing carriages, since a carriage can beremoved and replaced without any disassembly of the carriage itself.

Returning to FIGS. 2 and 3, the train 14 of carriages is formed of aplurality of lower level carriages 50 and a plurality of upper levelcarriages 51. Both types of carriages 50 and 51 have a frame 52 in theshape of an elongate "C", which wraps around the monorail with the openside of the "C" facing the posts 30 and receiving the monorail 12 andsupport brackets 32. The frame 52 may be constructed of bent steel oranother metal such as aluminum, or formed of any suitably strongmaterial. Four axle bolts 54, shown in FIGS. 3 and 4, extend across theframe 52, two axles on either side of the monorail 12. Four groovedrollers 55 are rotatably mounted on the axles 54 so as to engage theupper and lower sides of the monorail 12 with the corners of themonorail being received in the grooves of the rollers. The rollers 55are provided with ball bearings (not shown) and preferably are made ofurethane for noise reduction, but can be constructed of metal. Spacers57 on either side of the rollers center the rollers within the frame 52.The axles and rollers are positioned so that the rollers snugly fit ontothe monorail 12 in a manner which permits free rotation of the rollersand smooth travel of the carriage along the monorail 12, without excessvibration.

The train 14 of carriages 50 and 51 preferably alternates upper andlower level carriages and completely fills the looped monorail 12 withcarriages. In such a configuration, it is not necessary to physicallyconnect the carriages to one another. Rather, a bumper 58, as shown inFIG. 4, may be fixed to one end of each carriage to cushion its contactwith the adjacent carriage. If the monorail is not completely filled byan even or odd number of carriages, the extra space can be filled by alarge bumper on one of the carriages or by a filler carriage having aspecial length. In an alternate embodiment, described below, thecarriages are resiliently attached to one another. Furthermore, itshould be understood that many advantages of the present invention canbe incorporated in a monorail system which is not a closed loop. Also,the carriages might move in reversible directions, or the monorail couldchange elevation along its course or follow a serpentine path.

The lower level carriages 50 and upper level carriages 51 include manycommon structural characteristics. A lower level carriage 50 will bedescribed first, and the differences in the upper level carriage 51 willbe noted. Each lower level carriage 50 includes a tilting tray orplatform 60 pivotally mounted to the frame 52 for tilting about alongitudinal axis, that is, an axis along the monorail 12. The tray 60preferably is made of fiberglass but may be constructed of metal,plastic, or wood. The tray is preferably rectangular and longitudinallyconcave toward its center to cause automatic centering of parcels asthey are loaded onto the tray.

A pair of pivot brackets 62 extend downwardly from the bottom of thetilting tray 60 and are attached by pivot pins 65 to a correspondingpair of pivot brackets 63 extending upwardly from the top of the frame52. The position of the tilting tray 60 is controlled by a detentmechanism 67, which includes a detent housing 68 projecting downwardlyfrom the center of the tilting tray 60 between the pivot brackets 62. Adownwardly opening cavity 69 in the detent housing 68 receives aspring-loaded square tube 70 which carries a cam follower 72 that ismovable against the pressure of the spring 70. As best shown in FIG. 3,a tray alignment cam 74 is mounted to the top of the carriage frame 52under the detent mechanism 67. The alignment cam 74 is shaped to have acentral recess 76, an outer recess 77 separated from the central recessby a hump 78, and an inner recess 79 separated frown the central recessby a hump 80.

The sides of each tilting tray 60 are bent down to define a pair of traytilting cam surfaces 85 along the longitudinal side edges. The profileof the cam surfaces 85 is shown in FIGS. 6 and 7. The cam surfaces slopedownwardly away from the leading end of the tray 60 (defined withrespect to the direction of travel of the carriage) to a low point atthe trailing end of the tray. When sufficient force is exerted on theside edges of the tray 60 via the cam surfaces 85 by the tray tiltingmechanisms 22, the force of the spring 70 is overcome and the follower72 crosses one of the humps 78 or 80. The force of the spring 70 thencauses the tray to continue tilting until the follower 72 rests in thecenter of either the inner recess 79 or the outer recess 77 depending onwhich way the tray has been tilted.

If the monorail sorting system has a reversible direction drive, thetray tilting cam surface will have a profile 87 as shown in FIG. 8. Asshown, the cam surfaces slope from both the leading and trailing ends ofthe tray 60 downwardly to a low point at the center of the tray.

Each upper level carriage 51 includes an upper level tilting tray 90which is elevated above the frame 52 by a tray elevation post 92. Theheight of the upper trays 90 can be varied, but preferably is eighteeninches or more. A cross beam 93 attached to the elevation post 92extends in a longitudinal direction and carries the pivot bracket 63 andthe tray alignment cam 74, which have the same structure as provided fora lower level carriage 50. The upper level trays 90 also include camsurfaces 85 for tilting and a detent mechanism 67 identical to thatprovided for lower level carriages.

In the preferred embodiment, the upper level tilting trays 90 extendlongitudinally over adjacent lower level trays 60. Also, the lower leveltrays 60 of every other carriage extend longitudinally over adjacentcarriages, beneath the upper level trays 90. The preferred configurationof adjacent carriages and upper and lower level trays can be seen inFIGS. 2 and 4. This configuration has great advantages in that a greaterdensity of items or parcels can be carried per unit length of monorail,reducing the square footage of floor space needed to house the monorailsorting system for a given desired rate of item handling. Furthermore,if the monorail must make tight turns, the carriages individually can beshort, such as about one foot long, while the trays may be almost twicethe length of the carriages. Preferably, about four inches clearance isleft between adjacent trays to allow for support posts and angling onturns.

The drive mechanism 16 is best shown in FIGS. 2 and 3. It provides asimple and reliable way to move the carriages around the monorailwithout complex chains, belts or gears as used in prior sortingmechanisms. A drive roller 102, preferably an inflated tire about twofeet in diameter, is rotatably mounted on a shaft (not shown) passingthrough a shaft carrier 103 below the carriage frames 52. The shaftcarrier 103 is pivotally connected to one of the posts 30 abouthorizontal pivot pins 105 aligned with a pivot axis parallel to themonorail 12. The shaft carrier 103 then extends beyond the post 30 intoa speed reducer 107 associated with an electric motor 108 for drivingthe shaft.

It will thus be seen that the drive connection between the drivemechanism 16 and the train 14 of carriages 50 and 51 is simply thefrictional contact between the outer surface of the tire 102 and thelower surfaces of the carriages. Since the heavy motor 108 iscantilevered at the end of the shaft carrier 103 opposite the tire 102,the weight of the motor 108 urges the tire 102 against the carriageframe 52. The outer periphery of the tire 102 preferably consists of ahigh friction elastomeric material or tread.

The drive mechanism 16 can be mounted at any location around themonorail loop, and several identical assemblies may be used with onemonorail loop in order to provide redundancy and to even out thepropulsion forces. As shown in FIG. 4, the tire as it rotates engagesone carriage after the other and propels the entire carriage train 14forward at an appropriate speed, which may be about 300 fpm. In order toprovide a reversible capability for the carriage train 14, it is onlynecessary to provide a reversible motor.

Referring now to FIG. 9, the input section 18 includes a lower inputconveyor 112 and an upper input conveyor 113. The conveyors 112 and 113are short metering conveyor assemblies that ate intermittently operableunder the control of the computer controller. A pair of stabilizingrails 115, one on each side of the monorail 12, extend just below eachtilting tray 60 and 90. The rails 115 are supported by members (notshown) extending upwardly from the floor or from the posts 30. Theconveyors 112 and 113 extend to a position closely adjacent to the outerside of the tilting trays, so that parcels 114 can be delivered onto thetrays. The stabilizing rails 115 prevent the trays from tilting as aresult of the impact and weight of the parcels 114. Thereafter, thedetent mechanism 67 is sufficient to keep the tray horizontal until thetray is tilted to discharge a parcel. If desired, rollers or wheelspositioned below the trays may be used to stabilize the trays duringloading instead of the rails 115.

The carriage tracking station 26 is located immediately downstream ofthe input section 18. As shown in FIG. 2, a handshake photocelltransmitter and detector 118 are positioned across the path of thecarriages. The photocell 118 detects the passage of each carriage andprovides an appropriate signal to the controller. A shaft encoder 120includes a wheel which engages the bottom of the carriage frames 52 andprovides an output signal corresponding to the distance traveled by thecarriages along the monorail. The role of these components in trackingloaded carriages to the proper output chutes will be described in detailbelow.

Details of the tray tilting mechanisms 22 are shown in FIGS. 3 and 5.Each mechanism 22 consists of a two-position cam following assemblywhich may be mounted to engage one of the cam surfaces 85 of either thelower trays 60 or the upper trays 90. As shown in FIG. 3, a lowertilting cam follower 125 is rotatably mounted on a shaft 126 that isrigidly connected to a vertical arm 128. The arm 128 is suspended fromabove the monorail 12 on a pivot 129. A solenoid 130 has an extendingplunger pivotally connected at 132 to the arm 128. A spring 133 normallydraws the arm 128 and cam follower 125 into the retracted position shownin FIG. 3, whereas operation of the solenoid 130 rotates the camfollower 125 into an operative position as shown in FIG. 5, in the pathof the cam surfaces 85. Alternately, it would be possible to employ aconventional solenoid of the type which is stable in both positions,eliminating the need for the spring 133.

Referring to FIG. 2, a tray tilting mechanism 22 positioned in the pathof the lower tray 60 is shown along side such a mechanism suspended at aheight in the path of the upper trays 90. The latter mechanism includesa shorter suspending arm 136 and a cam follower 135. Whether positionedto tilt upper or lower trays, the mechanisms 22 are constructed andoperate in a similar manner. FIGS. 6 and 7 show the action of the camfollower 125 on the cam surface 85 as the tray 60 moves to the right.The side of the tray engaging the cam follower 125 is lifted by thepressure of the cam follower 125 on the cam surface 85. As noted above,this action tilts the tray until the follower 72 of the detent mechanism67 leaves the central recess 76 of the tray alignment cam 74.

Details of the output sections 20 may be seen in FIGS. 2 and 10. Loweroutput chutes 140 and upper output chutes 141 are positioned along bothsides of the monorail 12 and are aligned to receive parcels sliding offthe trays 60 and 90, respectively, when such trays have been tilted byone of the tilting mechanisms 22. A tilting mechanism 22 is associatedwith each output chute 140 and 141. If a parcel 114 is destined for anoutput chute 141 on the inside of the monorail 12, the cam surface 85 onthe outside of the monorail 12 will be engaged by a cam follower 135just before the carriage holding the parcel reaches the output chute.The cam follower 135 will cause the detent mechanism 67 to jump into theouter recess 77 of the tray alignment cam, and the tray 90 will tilt tothe inside of the monorail, into the position shown in FIG. 10. The traytilts to enough of an angle (preferably about 15°) that the parcel 114will slide off the tray onto the output chute 141 under the force ofgravity. If the parcel is destined for one of the output chutes on theoutside of the monorail, the tray is tilted so that the detent mechanismis moved to the inner recess 79 of the cam 74, tilting the tray to theoutside in alignment with an output chute 140, as shown in connectionwith the lower tray 60 shown in FIG. 10.

As the carriages approach the input section 18, most or all of the trays60 and 90 will have been tilted by the tray tilting mechanisms 22. Inorder to prepare the trays for the receipt of new parcels, the trayreturn mechanism 24, shown diagrammatically in FIG. 2, is positionedupstream of the input section 18. Four fixed tray return rollers 145 aremounted on fixed support arms 147 to position the rollers 145 in thepath of the cam surfaces 85 of the trays 60 and 90 in all four possibletilted orientations of the trays. The rollers 145 act as cam followersin the manner shown in FIGS. 6 and 7, and cause the detent mechanisms toreturn to the central recess 76 of the tray alignment cam 74. Thisoccurs before the trays pass over the stabilizing rails 115 describedabove. Alternatively, fixed ramps may be used for the tray returnfunction in lieu of the rollers 145.

An optional linkage 150 for connecting adjacent carriages as shown inFIGS. 11-13. A roughly Z shaped bracket 152 is attached to the innerside of each carriage frame 52 at both ends of the carriage. Thebrackets are mounted to define a pocket opening toward the next adjacentcarriage, and are aligned so that such openings face one another. Anelastomeric bumper 154 is shaped to define two enlarged ends 155 and acentral bumper protrusion 156 which extends outwardly between the ends155. As shown in FIG. 13, the bumper 154 is slidably inserted under thebrackets 152 of two adjacent carriages, so that the enlarged ends 155are received in the facing pockets defined by the brackets 152. At thesame time, the protrusion 156 is inserted between the ends of thecarriage frames 52 to provide a bumper cushion between the carriages.

An example of the positioning of a linkage 150 is shown in FIG. 2. Sincethe bumper member 154 is formed from rubber or some other pliablematerial, and is positioned around the interior of the carriage train114, the linkages 150 are able to flex as the carriages pass aroundcurves of the monorail 12. This enables the carriages to be linked andcushioned from one another without the need for mechanical joints,hinges, or the like.

SECOND EMBODIMENT

An alternate embodiment of the present invention is shown in FIGS.17-20, which portray a suspended automatic sorting system 160. Incontrast to the support post 30 of the first embodiment, downwardlyextending posts 162 suspend the monorail 12 from a ceiling or otheroverhead support structure. As shown in FIG. 18, the alternate drivemechanism includes a drive tire 165 mounted on a shaft carrier 166 whichis pivotally connected at a pivot 168 associated with a suspending post162. However, the drive tire 165 rests on the upper surface of thecarriage frames 52, and a drive motor 170 is attached to the drive shaftcarrier 166 on the side of the drive tire 165 opposite to the post 162.Thus, the weight of the motor 170 presses the drive tire 165 downagainst the carriage frames 52.

The purpose of the suspended sorting system 160 is to carry large orirregular items on suspended tray assemblies 175 hanging below thecarriages frames 52. Each carriage has a basic frame 52 and system ofrollers 55 which surround and engage the monorail 12 in the same manneras described above in connection with the first embodiment. Eachsuspended tray assembly 175 includes a pair of suspending arms 177 whichare L-shaped as shown in FIG. 18. The suspending arms 177 for a trayassembly 175 may be attached to carriage frames 52 which are separatedby one or more filler carriages, in order to provide a carrying surfacethat is longer than a tray capable of being supported by a singlecarriage.

In the variation shown in FIG. 18, a platform 178 is supported by a pairof suspending arms 177. The vertical member of the suspending arms isattached at the inner, lower corner of carriage frame 52 by aspring-catch hinge 181. The hinge 181 is of a conventional constructionwhich holds its position until rotated a short distance upwardly, afterwhich it releases to rotate downwardly past its initial holdingposition. In this embodiment, the tray tilting mechanism includes aroller 182 which may be moved between a retracted position and anextended position in the path of the platforms 178, by a mechanismsimilar to that used to operate the cam follower 125 in the firstembodiment. Alternately, the roller 182 could be movable from aretracted position directly below the path of the carriages. Theplatform 178 may be provided with a bevelled leading edge 179 forinitial engagement by the roller 182. The roller 182 is positioned sothat it lifts the platform 178 a short distance to disengage thespring-catch hinge 181 as the platform "climbs" the roller. After theplatform 178 clears the roller 182, the weight of the platform and anitem 184 on the platform moves the platform downwardly into a positionshown in phantom lines in FIG. 18. This lower position is in alignmentwith an output chute 140 which guides the item 184 to its destination.

Another variation of the suspended tray assembly is shown in FIG. 19.Here, suspending arms 185 are rigidly attached to the inner surface ofthe carriage frames 52, and the platform 178 is provided withconventional motorized rollers 186 to provide a conveyor bed. Themotorized rollers 186 are energized as the platform 178 is aligned withthe correct output chute 140 to transport the item 184 off of theplatform 178 onto the chute 140. This energization is accomplished byproviding a pair of sweep contacts 190 on either the suspending arms185, the platform 178, or the carriage frame 52. The contacts 190 arewired (not shown) to the motorized rollers 186. A pair of mating supplycontacts 192 is mounted on support structure (not shown) in the path ofthe sweep contacts 190. A set of the supply contacts 192 may beassociated with each output chute 140. The computer controllerselectively provides power to the correct set of contacts when aplatform 178 carrying an item destined for the output chute 140approaches. Or, the supply contacts may be mounted to be movable intothe path of the sweep contacts when a particular platform 178 isapproaching the output chute 140 onto which the item on the platform isto be unloaded. A solenoid actuating system of the type shown inconnection with the tilting mechanisms 22 of the first embodiment couldbe used to move the supply contacts 192. Typically, a 12 or 24 voltpower supply is required for the motorized rollers 186.

A third variation of the suspended tray assembly is shown in FIG. 20, inwhich the motorized roller bed 186 of FIG. 19 has been replaced by amotorized conveyor belt 195 having drive rollers at either end.Operation of the conveyor belt to unload items from a platform 178 maybe accomplished using contacts 190 and 192 as described above.

By extending the suspended tray assembly 175 below three or morecarriages, it may be made long enough to carry large, bulky andirregular items. For example, the tray may be three to four feet longand 18 inches wide. The length depends on the number and size of thefiller carriages positioned between the carriages which support thesuspending arms. The suspended tray assembly 175 is also more practicalfor carrying heavy loads because such loads are easier to hang than tosupport on a platform from below.

OPERATION

The automatic sorting system 10 or 160 is operated under the control ofa digital controller, which may be a programmed logic controller (PLC)or a general purpose microprocessor such as found in a personalcomputer. Methods for programming such controllers to operate a sortingsystem of the type disclosed herein are conventional and known to thoseskilled in the art. A flow chart of the general logic to be programmedinto the controller is shown in FIG. 21.

The number of carriages and an identification code for each carriage areinput into the controller memory, along with the identification of thecarriage that is initially aligned with each input conveyor whenmovement of the carriage train begins. After the carriage train 14starts, it moves continuously along the monorail 12. An operator placesthe packages 114 in single file order on one of the input conveyors 112or 113. The operator then reads the label on each package and enters thedestination zip code into the controller memory, as noted at Block 1 ofthe flow chart, using either a keypad or a voice recognition inputdevice. As the carriage train 14 moves around the monorail 12, the shaftencoder 120 provides a signal representing its count to the controller,which is then able to determine at any given time the location of thecarriages.

At Block 2 the zip code entered at Block 1 is stored in a sequentiallist. At Block 3, the controller calculates the number of encoder pulsesthat will occur between the location of the photocell 18 and thedestination output chute 140 or 141 that is associated with the enteredzip code. At Block 4, the controller checks its memory to determinewhether the status of the next tray approaching the input conveyor is"empty" or "full." If the next tray is not empty, the controller holdsoperation of the input conveyor until it has an opportunity to check thenext tray. If the approaching tray is empty, in Block 6 a signal is sentto operate the input conveyor to load the tray. The input conveyors areconfigured to operate rapidly and intermittently on command from thecontroller, which starts operation of the input conveyor shortly priorto the time at which the continuously moving carriage becomes alignedwith the input conveyor. As the parcel 114 moves onto the tilting tray60 or 90, the concave shape of the tray helps to center the parcel in astable position.

Upon commanding operation of the input conveyer, the controller alsochanges the status of the particular tray to "full" in memory andassociates the next zip code in the sequential list with the particulartray (Block 7). If desired, a photocell or other sensor can be placedbetween the input conveyor and the carriages to determine whether infact a parcel has been delivered to the tray upon operation of the inputconveyor. As the now-loaded carriage continues to move, its passage isdetected by the photocell 118, which is located just downstream of theinput conveyor, as noted in Block 8 of the flow chart. The photocellprovides a signal corresponding to the encoder count at the time thecarriage passes to the controller, where the count is stored. At Block9, the previously calculated number of pulses between the photocell andthe destination output chute are added to the current encoder count toprovide the count that will be reached when it is necessary to unloadthe parcel. This value is stored in association with the particulartray.

In order to account for any drifting of the carriages as they travelaround the monorail 12, one or more additional photocell detectors 121may be provided along the monorail path. At Block 10, the output signalfrom an additional photocell is checked to determine whether thecarriage in question passes the additional photocell at precisely theencoder count corresponding to the position at which the carriage shouldbe found. If there is a variation from the predicted count, the storedunload count associated with the carriage is updated to reflect thechange. If the lack of correspondence is greater than a predeterminedthreshold, the carriage may be rerouted to an unsorted output chute forresorting.

At Block 11, the controller, upon receiving the unload count from theshaft encoder, sends a signal to operate the tilting mechanism 22associated with the output chute assigned the destination zip code.Tilting begins shortly before complete alignment of the tray 60 or 90with the output chute 140 or 141, so that movement is imparted to theparcel 114 at the proper time for the parcel to slide off the tray ontothe output chute. Any number of trays can be tilted simultaneouslydepending on when they reach the location of the unload count. At thistime, as noted in Block 12, the memory record associated with the traymay be cleared of values associated with the sorted parcel and the traystatus changed to "empty."

As noted above, the trays remain tilted until the trays pass through thetray return mechanisms 24, which returns the trays to their horizontalposition without intervention by the controller. The process outlined inFIG. 21 is repeated when the tray returns to the input section 18.

It is possible to operate the system with multiple input conveyors, witheach of the input conveyors having a photocell detector 118 associatedwith it to signal the location of a carriage that has just received aparcel from the input conveyor. This permits the unload count for thecarriage to be determined. It would be possible to alter the programmedlogic to cause input conveyors positioned upstream of other inputconveyors to skip empty carriages in a coordinated fashion to allow allof the input conveyors to continue loading their parcels. Of course,upper and lower input conveyors 113 and 112 can operate virtuallysimultaneously.

From the foregoing description, it will be seen that an automaticsorting system embodying the present invention provides a highthroughput of parcels to be sorted, using a system that is simple inconstruction, is easy to maintain and keep on line, and occupies arelatively small amount of space. The system also operates at low noiselevels. In particular, the efficiency of the system is improved by theuse of a multi-level tray system associated with carriages running alongone track. The novel drive mechanism moves the carriages in a reliablemanner without the need for complex belt or chain drives. Furthermore,the carriages may optionally be linked by the low-noise, pliable linkageassembly described above.

While the present invention in its various aspects has been described indetail with regard to preferred embodiments thereof, it should beunderstood that variations, modifications and enhancements can be madeto the disclosed apparatus and procedures without departing from thespirit and scope of the present invention as defined in the appendedclaims.

What is claimed is:
 1. An apparatus for transporting and sortingobjects, each to one of a plurality of output locations, comprising:atrack having at least one curve therein; a plurality of carriagesmounted adjacent to one another for movement along said track; a drivemechanism comprising:a drive roller mounted adjacent to said track tofrictionally engage said carriages in sequence; and a source ofrotational force mounted to rotate said drive roller so as to cause saidcarriages to move along said track; a transfer mechanism operative tounload an object from said carriages; a linkage connecting adjacentcarriages, said linkage comprising a pliable, deformable member attachedto each of said adjacent carriages and extending between said adjacentcarriages, said linkage working to both connect and cushion adjacentcarriages and allow flexing when said carriages move around said curve;at least one sensor located to monitor the position of each of saidcarriages along said track; and a programmed controller configured tooperate said transfer mechanism responsive to said sensor to unload acarriage carrying an object when said carriage reaches a predeterminedoutput location along said track.
 2. The apparatus of claim 1, whereinsaid track is at closed loop and said carriages form a closed loop. 3.The apparatus of claim 1, wherein said linkage comprises a bracketattached to each of said adjacent carriages, said bracket being shapedto define a pocket; and a link member defining a pair of ends positionedin said pockets.
 4. The apparatus of claim 3, wherein said brackets arepositioned on side surfaces of said carriages, and said link memberincludes a cushioning member extending between end surfaces of saidcarriages.
 5. The apparatus of claim 1, wherein said drive mechanismcomprises a pair of said drive rollers spaced apart from one another. 6.The apparatus of claim 1, wherein said source of rotational forcecomprises a motor connected to said drive roller by a drive shaftpivotally mounted about an axis located intermediate said drive rollerand said motor; said drive roller and said motor being movable with saiddrive shaft such that the weight of said motor urges said drive rolleragainst said carriages.
 7. The apparatus of claim 1, wherein at leastone of said carriages is an upper level carriage including a carriagebody engaging said track and an upper object-holding platform spacedabove said body.
 8. The apparatus of claim 7, wherein two carriagesadjacent to opposite ends of said upper level carriage are lower levelcarriages each including a carriage body engaging said track and a lowerobject-holding platform positioned below the level of said upperplatform.
 9. The apparatus of claim 8, wherein said upper platformextends at least partly over said lower platforms of said adjacent lowerlevel carriages.
 10. The apparatus of claim 8, further comprising aninput conveyor mechanism capable of depositing objects on said upper andlower platforms.
 11. The apparatus of claim 8, further comprising atleast one upper input conveyor positioned to deposit objects on saidupper platform and at least one lower input conveyor positioned todeposit objects on said lower platform.
 12. The apparatus of claim 1,wherein said carriages include a carriage body engaging said track and aplatform pivotally mounted to said carriage body, said platform defininga cam surface; and wherein said transfer mechanism comprises a camfollower selectively positionable in the path of said cam surface. 13.The apparatus of claim 12, wherein said carriages comprise a detentpositioned on one of said platform and said carriage body, operable withat least two depressions located in the other of said platform and saidcarriage body to maintain said platform in a level orientation prior tooperation of said transfer mechanism and in a tilted orientationfollowing operation of said transfer mechanism.
 14. The apparatus ofclaim 13, further comprising a platform return mechanism operable toreturn said platforms from a tilted to a level orientation.
 15. Theapparatus of claim 14, further comprising an input conveyor mechanismcapable of depositing objects on said platforms; and wherein said returnmechanism is positioned to operate prior to said carriages approachingsaid input conveyor mechanism.
 16. The apparatus of claim 1, whereinsaid drive roller comprises a resilient material around its periphery.17. The apparatus of claim 1, wherein said drive roller comprises aninflated annular tube.
 18. The apparatus of claim 1, further comprisingan object-holding platform suspended below at least two of saidcarriages, said transfer mechanism being operative to unload an objectfrom said object-holding platform.
 19. An apparatus for transportingobjects, comprising:a track; a plurality of carriages each including acarriage body mounted for movement along said track, at least one ofsaid carriages being an upper level carriage including only an upperobject-holding platform defining a cam surface and being at a fixedheight which is spaced above said body, and at least one of saidcarriages being a lower level carriage including only a lowerobject-holding platform defining a cam surface and being at a fixedheight which is below the level of said upper platform, said carriagesbeing arranged to alternate upper and lower level carriages; a firsttransfer mechanism comprising a cam follower which is selectivelypositionable in the path of said cam surface for said upperobject-holding platform; a second transfer mechanism comprising a camfollower which is selectively positionable in the path of said camsurface for said lower object-holding platform: and a drive mechanismoperable to cause said carriages to move along said track.
 20. Theapparatus of claim 19, wherein said upper platforms extend at leastpartly over said lower platforms of adjacent lower level carriages andsaid lower platforms extend at least partly over said upper levelcarriage bodies.
 21. The apparatus of claim 19, further comprising aninput conveyor mechanism capable of depositing objects on said upper andlower platforms.
 22. The apparatus of claim 19, wherein said platformsare pivotally mounted to said carriage bodies, and define a cam surface;and further comprising a transfer mechanism, operative to unload anobject from said carriages, including a cam follower selectivelypositionable in the path of said cam surface.
 23. The apparatus of claim22, wherein said carriages comprise a detent positioned on one of saidplatform and said carriage body, operable with at least two depressionslocated in the other of said platform and said carriage body to maintainsaid platform in a level orientation prior to operation of said transfermechanism and in a tilted orientation following operation of saidtransfer mechanism.
 24. The apparatus of claim 24, further comprising aplatform return mechanism operable to return said platforms from atilted to a level orientation.
 25. The apparatus of claim 24, furthercomprising an input conveyor mechanism capable of depositing objects onsaid platforms; and wherein said return mechanism is positioned tooperate prior to said carriages approaching said input conveyormechanism.
 26. An apparatus for transporting objects, comprising:atrack: a plurality of carriages each including a carriage body mountedfor movement along said track, at least one of said carriages being anupper level carriage including an upper object-holding platform spacedabove said body, and at least one of said carriages being a lower levelcarriage including a lower object-holding platform positioned below thelevel of said upper platform, said carriages being arranged to alternateupper and lower level carriages and said upper platforms extending atleast partly over said lower platforms of adjacent lower level carriagesand said lower platforms extending at least partly over said upper levelcarriage bodies; and a drive mechanism operable to cause said carriagesto move along said track.
 27. An apparatus for transporting and sortingobjects, each to one of a plurality of output locations, comprising:atrack; a plurality of carriages mounted adjacent to one another formovement along said track; a drive mechanism comprising:a drive rollermounted adjacent to said track to frictionally engage said carriages insequence; and a source of rotational force mounted to rotate said driveroller so as to cause said carriages to move along said track, saidsource of rotational force comprising a counterbalance connected to saiddrive roller by a drive shaft pivotably mounted about an axis locatedintermediate said drive roller and said counterbalance, said driveroller and said counterbalance being movable with said drive shaft suchthat the weight of said counterbalance urges said drive roller againstsaid carriages; a transfer mechanism operative to unload an object fromsaid carriages; at least one sensor located to monitor the position ofeach of said carriages along said track; and a programmed controllerconfigured to operate said transfer mechanism responsive to said sensorto unload a carriage carrying an object when said carriage reaches apredetermined output location along said track.
 28. The apparatus ofclaim 27, wherein said counterbalance comprises a motor drivinglyconnected to said drive roller.
 29. An apparatus for transporting andsorting objects, each to one of a plurality of output locations,comprising:a track; a plurality of carriages mounted adjacent to oneanother for movement along said track; a drive mechanism comprising:adrive roller mounted adjacent to said track to frictionally engage saidcarriages in sequence; and a source of rotational force mounted torotate said drive roller so as to cause said carriages to move alongsaid track; a transfer mechanism operative to unload an object from saidcarriages; a linkage connecting adjacent carriages, said linkagecomprising a bracket attached to each of said adjacent carriages, saidbracket being shaped to define a pocket and a link member defining apair of ends positioned in said pockets; at least one sensor located tomonitor the position of each of said carriages along said track; and aprogrammed controller configured to operate said transfer mechanismresponsive to said sensor to unload a carriage carrying an object whensaid carriage reaches a predetermined output location along said track.30. The apparatus of claim 29, wherein said brackets are positioned onside surfaces of said carriages, and said link member includes acushioning member extending between end surfaces of said carriages. 31.An apparatus for transporting and sorting objects, each to one of aplurality of output locations, comprising:a track; a plurality ofcarriages, each defining a cavity for receiving the track and alow-friction contact surface for engaging the track, and being mountedadjacent to one another for movement along said track; a drive mechanismcomprising:a drive roller mounted adjacent to said track to frictionallyengage said carriages in sequence, the frictional engagement of saidroller being removed from said contact surface on said carriages; and asource of rotational force mounted to rotate said drive roller so as tocause said carriages to move along said track; a transfer mechanismoperative to unload an object from said carriages; at least one sensorlocated to monitor the position of each of said carriages along saidtrack; and a programmed controller configured to operate said transfermechanism responsive to said sensor to unload a carriage carrying anobject when said carriage reaches a predetermined output location alongsaid track.
 32. The apparatus of claim 31, wherein said low-frictioncontact surface comprises rollers positioned to engage said track. 33.An apparatus for transporting objects, comprising:a track; a pluralityof carriages each including a carriage body mounted for movement alongsaid track, at least one of said carriages being an upper level carriageincluding an upper object-holding platform spaced above said body, andat least one of said carriages being a lower level carriage including alower object-holding platform positioned below the level of said upperplatform, said carriages being arranged to alternate upper and lowerlevel carriages and said upper platforms extending at least partly oversaid lower platforms of adjacent lower level carriages; and a drivemechanism operable to cause said carriages to move along said track.